The emergence of COVID-19 started scientists on a yearlong crash course to learn how the coronavirus might travel through the air and how to stop it. They learned a lot, and quickly.

Gyms are reopening with fewer people and more protocols, and they want to rehabilitate their pandemic-battered image. Although there's not much evidence, they say the science is on their side.

Studies show children have lower rates of COVID-19 and have milder symptoms than adults. But there's less information on how much kids spread the coronavirus, which is key to safely reopen schools.